Use Single Use Lock instead of secp256k1 lock to mint xUDT for examples

[duanyytop]

Single Use Lock is similar to TypeID, using the uniqueness of the CKB out point to ensure the cell can only be unlocked once. It can be used for limited issuance of xUDT.

Now the xUDT example of rgbpp-sdk uses the secp256k1_blake160 lock to issue xUDT, which cannot ensure limited issuance. Therefore, using Single Use Lock to issue xUDT will better meet the needs of most Dapps.